Thin-film, solid state, rechargeable lithium, lithium-ion and lithium-free batteries can be produced with a thickness of less than 15 micrometers. Such batteries have high energy and power densities, can be cycled thousands of times, and can be fabricated in arbitrary shapes and to any required sizes. These batteries can be fabricated on any solid substrate such as silicon, alumina, glass and plastics. They can also be fabricated on flexible substrates such as flexible plastics and thin metal foils.
FIG. 1 is a generalized top view of a thin-film battery provided on a substrate 11 according to the prior art.
FIG. 2 is a cross sectional view taken along line 2-2 of FIG. 1. In the examples of FIGS. 1 and 2, the thin-film battery is a lithium-ion battery having an exposed conductive pad 13 for providing electrical connectivity to the cathode, and a further exposed conductive pad 15 for providing electrical connectivity to the lithium-ion anode.
Thin-film batteries have a wide range of uses as active or standby power sources for consumer products such as non-volatile memories, smart cards, sensors, radio frequency identification tags, micro-sized devices, implantable medical devices, miniature transmitters, MEMS devices and PCMCIA cards. In prior art applications, thin-film batteries have been integrated with multi-chip modules by fabricating the thin-film battery onto the backside of the multi-chip module's ceramic package. The battery is connected to the multi-chip circuitry on the front side of the package by depositing the cathode and anode current collectors of the battery over conductive through-holes.
Thin-film lithium-ion and lithium-free batteries, when not charged, are not adversely affected by heating to 250 degrees centigrade for 10 minutes. Many integrated circuits are assembled by the solder reflow or surface mount process in which all the electronic components are soldered on the board at the same time by heating to temperatures as high as 250 degrees centigrade for several minutes. Uncharged lithium-ion and lithium-free batteries can survive this assembly process, and can therefore be present on the board during the process.
It is desirable in view of the foregoing to provide further applications for thin-film batteries.
According to exemplary embodiments of the invention, an integrated circuit package has encapsulated therein an integrated circuit die and a thin-film battery electrically connected to the integrated circuit die.